Image capturing apparatus, image capturing method, and storage medium

ABSTRACT

There is provided an image capturing apparatus. An image capturing unit acquires a signal in a first acquisition mode or a second acquisition mode for each pixel of an image sensor. In the first acquisition mode, an image signal obtained by adding focus detection signals of a plurality of photoelectric conversion units of the pixel is acquired. In the second acquisition mode, the focus detection signals are acquired in addition to the image signal. The image capturing alternately captures a recording image and a focus detection image having a smaller number of pixels than the recording image, applies all pixels to the first acquisition mode when capturing the recording image, and applies at least a part of the pixels to the second acquisition mode when capturing the focus detection image.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image capturing apparatus, an imagecapturing method, and a storage medium.

Description of the Related Art

Conventionally, a technique is known that implements the acquisition ofa focus detection signal and the acquisition of an image signal by usingone image sensor. For example, a technique has been proposed in which apixel that acquires a focus detection signal serves also as a pixel foracquiring a displaying/recording image signal (see Japanese PatentLaid-Open No. 2001-083407). According to this technique, at least someof the pixels constituting an image sensor are divided into a pluralityof regions in at least one of a horizontal direction and a verticaldirection. At the time of image acquisition, an image signal can beobtained by adding signals obtained from the regions obtained bydivision. Also, at the time of focus adjustment, a phase differencefocus detection signal in which each pixel is pupil-divided can beobtained by performing read-out so as to obtain signals corresponding totwo regions obtained by division in the horizontal direction or thevertical direction.

Japanese Patent Laid-Open No. 2012-155095 discloses an image capturingapparatus in which signals of a plurality of regions obtained bydivision are read into a line memory, and switching is performed betweenthe following actions: adding the signals on a pixel-by-pixel basis soas to output the resulting signal as an image signal; and independentlyoutputting the signal corresponding to each region so as to use thesignal as a phase difference focus detection signal.

Here, consideration is given to processing in which continuous imagecapturing with autofocus (AF) tracking is performed by using an imagesensor as disclosed in Japanese Patent Laid-Open No. 2012-155095 thathas a pupil division readout function and in which each pixel iscomposed of a plurality of photoelectric conversion units. A focusdetection signal can be obtained by performing read-out so as to obtainsignals corresponding to two regions obtained by dividing each pixel inthe horizontal direction or the vertical direction, and it is thereforepossible to acquire both of a focus detection signal and an image signalby capturing one frame. That is, continuous image capturing can beimplemented by repeating exposure, acquisition of a focus detectionsignal and an image signal, and focus adjustment.

However, a larger noise is generated in the configuration in which bothof a focus detection signal and an image signal are acquired from thesame pixel than in a configuration in which only an image signal isacquired. Also, in the case of a configuration in which pixels thatacquire both of a focus detection signal and an image signal and pixelsthat acquire only an image signal are present in a mixed state such as aconfiguration in which only a partial region of the angle of view isused as a focus detection region, the noise level varies from region toregion in a captured image, which may deteriorate the image quality.This problem is particularly pronounced when image capturing isperformed under an image capturing condition in which a large noise isgenerated, such as at the time of image capturing with a highsensitivity.

In addition, the time required to capture a recording still image isrelatively long, and thus if focus control for performing second imagecapturing is performed based on a focus detection signal acquired byperforming first image capturing, the focus cannot follow a fast movingsubject, which may cause deterioration of image quality.

SUMMARY OF THE INVENTION

The present invention has been made under the circumstances describedabove, and the present invention provides a technique for suppressingdeterioration of image quality when continuous image capturing isperformed by using an image sensor that can acquire both of a focusdetection signal and an image signal from the same pixel.

According to a first aspect of the present invention, there is providedan image capturing apparatus comprising: an image sensor including aplurality of pixels, each pixel including a plurality of photoelectricconversion units that generate focus detection signals from light fluxthat have passed through different regions in an exit pupil in anoptical system; and an image capturing unit configured to continuouslycapture a plurality of images by using the image sensor, the imagecapturing unit being configured to acquire a signal in a firstacquisition mode or a second acquisition mode for each pixel, the firstacquisition mode being a mode in which an image signal obtained byadding the focus detection signals of the plurality of photoelectricconversion units is acquired, and the second acquisition mode being amode in which the focus detection signals are acquired in addition tothe image signal, wherein the image capturing unit is configured toalternately capture a recording image and a focus detection image havinga smaller number of pixels than the recording image, apply all pixels tothe first acquisition mode when capturing the recording image, and applyat least a part of the pixels to the second acquisition mode whencapturing the focus detection image.

According to a second aspect of the present invention, there is providedan image capturing apparatus comprising: an image sensor configured tooutput an image signal for generating an image and a focus detectionsignal for performing focus detection; and a control unit configured tocontrol a number of pixels used to output the image signal and the focusdetection signal from the image sensor and a predetermined region foroutputting the focus detection signal in the image sensor, wherein thecontrol unit is configured to, when successively acquiring frames fromthe image sensor, control the number of pixels used to output the imagesignal and the focus detection signal from the image sensor in a frameacquired between the successively acquired frames, based on an imagecapturing condition.

According to a third aspect of the present invention, there is providedan image capturing method for an image capturing apparatus comprising animage sensor including a plurality of pixels, each pixel including aplurality of photoelectric conversion units that generate focusdetection signals from light flux that have passed through differentregions in an exit pupil in an optical system, the method comprising:continuously capturing a plurality of images by using the image sensor,wherein a signal is acquired in a first acquisition mode or a secondacquisition mode for each pixel, the first acquisition mode being a modein which an image signal obtained by adding the focus detection signalsof the plurality of photoelectric conversion units is acquired, and thesecond acquisition mode being a mode in which the focus detectionsignals are acquired in addition to the image signal, wherein arecording image and a focus detection image having a smaller number ofpixels than the recording image are alternately captured, all pixels areapplied to the first acquisition mode when capturing the recordingimage, and at least a part of the pixels are applied to the secondacquisition mode when capturing the focus detection image.

According to a fourth aspect of the present invention, there is providedan image capturing method for an image capturing apparatus comprising animage sensor configured to output an image signal for generating animage and a focus detection signal for performing focus detection, themethod comprising: controlling a number of pixels used to output theimage signal and the focus detection signal from the image sensor and apredetermined region for outputting the focus detection signal in theimage sensor, wherein, when frames are successively acquired from theimage sensor, the number of pixels used to output the image signal andthe focus detection signal from the image sensor in a frame acquiredbetween the successively acquired frames is controlled based on an imagecapturing condition.

According to a fifth aspect of the present invention, there is provideda non-transitory computer-readable storage medium which stores a programfor causing a computer to execute an image capturing method for an imagecapturing apparatus comprising an image sensor including a plurality ofpixels, each pixel including a plurality of photoelectric conversionunits that generate focus detection signals from light flux that havepassed through different regions in an exit pupil in an optical system,the method comprising: continuously capturing a plurality of images byusing the image sensor, wherein a signal is acquired in a firstacquisition mode or a second acquisition mode for each pixel, the firstacquisition mode being a mode in which an image signal obtained byadding the focus detection signals of the plurality of photoelectricconversion units is acquired, and the second acquisition mode being amode in which the focus detection signals are acquired in addition tothe image signal, wherein a recording image and a focus detection imagehaving a smaller number of pixels than the recording image arealternately captured, all pixels are applied to the first acquisitionmode when capturing the recording image, and at least a part of thepixels are applied to the second acquisition mode when capturing thefocus detection image.

According to a sixth aspect of the present invention, there is provideda non-transitory computer-readable storage medium which stores a programfor causing a computer to execute an image capturing method for an imagecapturing apparatus comprising an image sensor configured to output animage signal for generating an image and a focus detection signal forperforming focus detection, the method comprising: controlling a numberof pixels used to output the image signal and the focus detection signalfrom the image sensor and a predetermined region for outputting thefocus detection signal in the image sensor, wherein, when frames aresuccessively acquired from the image sensor, the number of pixels usedto output the image signal and the focus detection signal from the imagesensor in a frame acquired between the successively acquired frames iscontrolled based on an image capturing condition.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of an image capturing apparatus 100.

FIG. 2 is a functional block diagram of the image capturing apparatus100.

FIG. 3 is a diagram schematically showing a configuration of one pixelincluded in an image capturing unit 22.

FIG. 4 is a diagram conceptually showing that light flux that havepassed through an exit pupil of a shooting lens 103 (optical system) areincident on the image capturing unit 22.

FIG. 5 is a diagram showing a readout region in the image capturing unit22 in image capturing sequence A.

FIG. 6 is a timing chart of image capturing sequence A.

FIG. 7 is a diagram showing a readout region in the image capturing unit22 for a live display still image (focus detection still image) in imagecapturing sequence B.

FIG. 8 is a timing chart of image capturing sequence B.

FIG. 9 is a flowchart of continuous image capturing processing performedby the image capturing apparatus 100.

FIG. 10 is a flowchart showing in detail image capturing sequenceselection processing performed in step S902 shown in FIG. 9.

FIG. 11 is a diagram showing an example of selecting an image capturingsequence based on sensitivity.

FIG. 12 is a diagram showing an example of selecting an image capturingsequence based on whether or not to execute black subtractionprocessing, sensitivity and temperature.

FIG. 13 is a diagram showing an example of selecting an image capturingsequence based on exposure time and temperature.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described withreference to the attached drawings. It should be noted that thetechnical scope of the present invention is defined by the claims, andis not limited by any of the embodiments described below. In addition,not all combinations of the features described in the embodiments arenecessarily required for realizing the present invention.

First Embodiment

FIG. 1 is an external view of an image capturing apparatus 100 accordingto a first embodiment. In FIG. 1, a display unit 28 displays images,various types of information, and so on. A shutter button 61 is anoperation unit for making a shooting instruction. A mode change switch60 is an operation unit for switching among various types of modes. Aconnector 112 connects a connection cable 111 and the image capturingapparatus 100. An operation unit 70 is constituted by operation memberssuch as various types of switches, buttons, a touch panel, and so onthat accept various types of operations from a user. A controller wheel73 is an operation member, included in the operation unit 70, that canbe rotationally manipulated. A power switch 72 is an operation unit forswitching the power on and off. A recording medium 200 is a recordingmedium such as a memory card, a hard disk, or the like. A recordingmedium slot 201 is a slot for holding the recording medium 200. Therecording medium 200 held in the recording medium slot 201 cancommunicate with the image capturing apparatus 100.

FIG. 2 is a functional block diagram of the image capturing apparatus100. In FIG. 2, a shutter 101 is a shutter having an aperture function.A shooting lens 103 corresponds to a lens group including a zoom lensand a focus lens. An image capturing unit 22 is an image sensorconstituted by a CCD, a CMOS element, or the like that converts anoptical image into an electrical signal. The image capturing unit 22includes an A/D conversion processing function. An AF evaluation valuedetection unit 23 calculates an AF (autofocus) evaluation value fromcontrast information and the like obtained from a digital image signal,and the obtained AF evaluation value is output from the image capturingunit 22 to a system control unit 50. A barrier 102 prevents an imagingsystem including the shooting lens 103, the shutter 101, and the imagecapturing unit 22 from being soiled or damaged by covering the imagingsystem. A flash 90 adds illumination light when shooting low-lightscenes, backlit scenes, or the like by emitting light during theshooting.

An image processing unit 24 carries out predetermined pixelinterpolation, resizing processes for reducing the size of an image andthe like, color conversion processing, and so on, on image data outputfrom the image capturing unit 22 or image data from a memory controlunit 15. The image processing unit 24 also performs predeterminedcomputational processing using captured image data, and the systemcontrol unit 50 performs exposure control and focus control based onresults obtained from these computations. A TTL (through-the-lens) AE(automatic exposure) process and an EF (automatic flash adjustment)process are implemented thereby. The image processing unit 24 alsocarries out an AF (autofocus) process, but at this time, the output fromthe AF evaluation value detection unit 23 in the image capturing unit 22is also sometimes used. The image processing unit 24 also performspredetermined computations using the captured image data, performing aTTL AWB (auto white balance) process based on the results thereof.

Data output from the image capturing unit 22 is written directly into amemory 32 via the image processing unit 24 and the memory control unit15, or via the memory control unit 15. The memory 32 stores the imagedata obtained by the image capturing unit 22 and subjected to A/Dconversion, image data for display in the display unit 28, and the like.The memory 32 is provided with a storage capacity sufficient to store apredetermined number of still images, a predetermined time's worth ofmoving images and audio, and so on. The memory 32 also functions as animage display memory (a video memory).

A D/A converter 13 converts data for image display, stored in the memory32, into an analog signal and supplies the analog signal to the displayunit 28. In this manner, image data for display written into the memory32 is displayed by the display unit 28 via the D/A converter 13. Thedisplay unit 28 carries out a display in a display device, which is anLCD or the like, based on the analog signal from the D/A converter 13.By using the D/A converter 13 to convert the digital signals A/Dconverted by the image capturing unit 22 and stored in the memory 32into analog signals and then sequentially transferring and displayingthose signals to the display unit 28, the display unit 28 functions asan electronic viewfinder and displays a through-the-lens image.

A non-volatile memory 56 is a memory that can be recorded to and erasedelectrically, and is constituted by, for example, a flash memory.Operational constants, programs, and so on of the system control unit 50are stored in the non-volatile memory 56. Here, “programs” refers toprograms for executing the various flowcharts according to the presentembodiment, which will be described later.

The system control unit 50 controls the image capturing apparatus 100 asa whole. The system control unit 50 implements the respective processesaccording to the present embodiment, mentioned later, by executingprograms recorded in the non-volatile memory 56 mentioned above. Thesystem control unit 50 also carries out display control by controllingthe memory 32, the D/A converter 13, the display unit 28, and so on. Asystem memory 52 is a RAM. Operational constants and variables of thesystem control unit 50, programs read out from the non-volatile memory56, and so on are loaded into the system memory 52. A system timer 53measures times used in various types of control, measures the time of aninternal clock, and so on.

The mode change switch 60, a first shutter switch 62, a second shutterswitch 64, and the operation unit 70 are operation members for inputtingvarious types of operating instructions to the system control unit 50.The mode change switch 60 switches an operating mode of the systemcontrol unit 50 among a still image shooting mode, a moving imageshooting mode, a playback mode, and so on. “Still image shooting mode”includes an auto shooting mode, an auto scene judgment mode, a manualmode, various types of scene modes having shooting settings for eachtype of shot scene, a program AE mode, a custom mode, and so on. Themode change switch 60 can switch the operating mode directly to one ofthese modes included in the still image shooting mode. Alternatively,the mode switch may be carried out by first switching to the still imageshooting mode using the mode change switch 60 and them using anotheroperation member to switch to one of the modes included in the stillimage shooting mode. Likewise, the moving image shooting mode may alsoinclude a plurality of modes. The first shutter switch 62 switches onpartway through the manipulation of the shutter button 61 provided inthe image capturing apparatus 100, or in other words, when the button isdepressed halfway (a shooting preparation instruction), and produces afirst shutter switch signal SW1. The system control unit 50 commencesoperations such as AF (autofocus) processes, AE (automatic exposure)processes, AWB (auto white balance) processes, and EF (automatic flashadjustment) processes in response to the first shutter switch signalSW1. The second shutter switch 64 turns on when the shutter button 61 iscompletely manipulated, or in other words, is fully depressed (ashooting instruction), and produces a second shutter switch signal SW2.The system control unit 50 commences a series of shooting processes,from reading out signals from the image capturing unit 22 to writingimage data into the recording medium 200, in response to the secondshutter switch signal SW2.

Functions relevant for different situations are assigned to theoperation members in the operation unit 70, which then act as varioustypes of function buttons, by making an operation for selecting varioustypes of function icons displayed in the display unit 28. An end button,a return button, a next image button, a jump button, a sort button, anattribute change button, and so on are examples of the function buttons.For example, a menu screen in which various types of settings can bemade is displayed in the display unit 28 when a menu button is pressed.A user can make various types of settings intuitively using the menuscreen displayed in the display unit 28, four directional (up, down,left, and right) buttons, a set button, and so on.

The controller wheel 73 illustrated in FIG. 1 is an operation member,included in the operation unit 70, that can be rotationally manipulated,and is used along with the directional buttons when specifying items tobe selected and so on. When the controller wheel 73 is rotationallymanipulated, an electrical pulse signal is produced in accordance withthe operational amount, and the system control unit 50 controls therespective units in the image capturing apparatus 100 based on thatpulse signal. An angle to which the controller wheel 73 has beenrotationally manipulated, a number of revolutions, and so on can bedetermined based on this pulse signal. Note that the controller wheel 73may be any kind of operation member as long as the member is capable ofdetecting rotational manipulation. For example, the controller wheel 73may be a dial-type operation member that produces a pulse signal uponthe controller wheel 73 itself rotating in accordance with a rotationalmanipulation made by a user. Alternatively, the controller wheel 73 maybe an operation member constituted by a touch sensor, with thecontroller wheel 73 detecting rotational motion of a user's finger onthe controller wheel 73 rather than the controller wheel 73 itselfrotating (a so-called “touch wheel”).

A thermometer 74 measures temperature of the image capturing apparatus100. A power control unit 80 is constituted by a battery detectioncircuit, a DC-DC converter, switch circuits for switching the blocksthrough which power passes, and so on, and detects whether or not abattery is connected, the type of the battery, the remaining batterypower, and so on. The power control unit 80 also controls the DC-DCconverter based on the detection results and instructions from thesystem control unit 50, and supplies a necessary voltage for a necessaryperiod to the various units, including the recording medium 200.

A power source unit 40 is a primary battery such as an alkali battery, alithium battery, or the like, a secondary battery such as a NiCdbattery, a NiMH battery, a Li battery, or the like, an AC adapter, andso on. A recording medium I/F 18 is an interface for the recordingmedium 200 such as a memory card, a hard disk, or the like. Therecording medium 200 is a recording medium for recording shot images,such as a memory card or the like, and is constituted by a semiconductormemory, a magnetic disk, or the like.

FIG. 3 is a diagram schematically showing a configuration of one pixelincluded in the image capturing unit 22. A pixel 22011 includes amicrolens 22012. Also, the pixel 22011 includes photodiodes (PD) thatserve as a plurality of photoelectric conversion units. In the exampleshown in FIG. 2, two PDs (PD 22013 and PD 22014) are illustrated, butthere is no limitation on the number of photodiodes as long as two ormore photodiodes are provided.

FIG. 4 is a diagram conceptually showing that light flux that havepassed through an exit pupil of the shooting lens 103 (optical system)are incident on the image capturing unit 22. In FIG. 4, referencenumeral 401 indicates a cross-section of a pixel array, and thecross-section 401 includes a microlens 402, a color filter 403, a PD 404and a PD 405. The PD 404 and the PD 405 correspond to the PD 22013 andthe PD 22014 shown in FIG. 3. Reference numeral 406 indicates the exitpupil of the shooting lens 103.

Here, the center of a light flux that has passed through the exit pupil406 and enters a pixel having the microlens 402 is defined as opticalaxis 409. The light flux that has passed through the exit pupil 406 isincident on the image capturing unit 22, with the light flux having theoptical axis 409 at the center. A region 407 and a region 408 arepartial regions of the exit pupil 406. Outermost light beams of a lightflux that has passed through the region 407 are indicated by referencenumerals 410 and 411, and outermost light beams of a light flux that haspassed through the region 408 are indicated by reference numerals 412and 413.

As can be seen from FIG. 4, among the light flux emitted from the exitpupil 406, those located above the optical axis 409 are incident on thePD 405, and those located below the optical axis 409 are incident on thePD 404. That is, the PD 404 and the PD 405 receive light flux that havepassed through different regions in the exit pupil 406. Here, the signalreceived by the PD 404 will be referred to as “image A”, the signalreceived by the PD 405 will be referred to as “image B”, and the sumvalue of image A and image B will be referred to as “image A+B”. Theimage capturing apparatus 100 can acquire distance information bycalculating the amount of defocus by acquiring the image A and the imageB (focus detection signals) and using these images as a pair of phasedifference signals. Also, the image capturing apparatus 100 can generatea still image based on image A+B (image signal) by acquiring the imageA+B. The image capturing apparatus 100 can perform signal read-out fromeach pixel included in the image capturing unit 22 by the following Xscheme or Y scheme.

X scheme (first acquisition mode): a read-out scheme for acquiring animage A+B

Y scheme (second acquisition mode): a read-out scheme for acquiring animage A, an image B, and an image A+B

In the case of the Y scheme, the image capturing apparatus 100 cangenerate an image B by, for example, reading out an image A and an imageA+B and then performing the following arithmetic calculation: “(imageA+B)−(image A)”. Alternatively, the image capturing apparatus 100 cangenerate an image A+B by reading out an image A and an image B and thenperforming the following arithmetic calculation: “(image A)+(image B)”.In the present embodiment, there is no particular limitation on thedetails of the read-out and the arithmetic calculation as long as animage A, an image B and an image A+B are acquired

Next, two image capturing sequences for performing continuous capturingof images that can be executed by the image capturing apparatus 100 willbe described with reference to FIGS. 5 to 8. The image capturingapparatus 100 can execute an image capturing sequence A (firstcontinuous image capturing mode) or an image capturing sequence B(second continuous image capturing mode), the image capturing sequence Abeing a sequence in which only recording still images are successivelycaptured, and the image capturing sequence B being a sequence in whichrecording still images and live display still images are alternatelycaptured.

FIG. 5 is a diagram showing a readout region in the image capturing unit22 in the image capturing sequence A. As shown in FIG. 5, the imagecapturing apparatus 100 performs read-out based on the Y scheme withrespect to some rows in the readout region (the rows being designated asstill image focusing pixels), and performs read-out based on the Xscheme with respect to the remaining rows. The read-out scheme asdescribed above in which the X scheme and the Y scheme are used incombination will be referred to as “X/Y scheme”. The image capturingapparatus 100 generates a recording still image based on an image A+Bacquired from each pixel in the readout region. Also, the imagecapturing apparatus 100 calculates the amount of defocus based on imagesA and images B acquired from the pixels applied to the Y scheme. Thatis, the image capturing apparatus 100 can acquire focus detectionsignals (phase difference signals) in addition to an image signal forgenerating a recording still image by performing image capturing inaccordance with the scheme shown in FIG. 5.

The image capturing apparatus 100 can also perform read-out based on theY scheme with respect to all of the pixels in the readout region.However, in this case, it takes time to perform the read-out, as aresult of which the speed of continuous image capturing decreases. Forthis reason, in FIG. 5, the configuration in which the X scheme and theY scheme are used in combination has been described. However, thepresent embodiment is not limited to the configuration in which the Xscheme and the Y scheme are used in combination. The read-out scheme canbe changed in real time, and thus the image capturing apparatus 100 maychange the pixels for which read-out is performed based on the Y scheme,according to the subject. It is thereby possible to enhance the accuracyof focusing.

FIG. 6 is a timing chart of the image capturing sequence A. The imagecapturing apparatus 100 starts read-out of an image capturing signalupon completion of accumulation of electric charges in an amountcorresponding to the set exposure time. In the sensor driving shown inFIG. 6, the hatched portions indicate the read-out based on the Yscheme. With respect to the pixels for which read-out is performed basedon the Y scheme, the image capturing apparatus 100 uses image A+B (imagesignal) to generate a recording still image, and uses image A and imageB (focus detection signal) to perform focusing processing (to calculatethe amount of defocus). The image capturing apparatus 100 drives thefocus lens during a period from the completion of the focusingprocessing to the next timing of image capturing (the timing of start ofan exposure period).

FIG. 7 is a diagram showing a readout region in the image capturing unit22 for a live display still image (focus detection still image) in theimage capturing sequence B. In general, a live display still image has asmaller number of pixels than that of a recording still image, and thusthe pixels to be read are thinned out at the time of capturing a livedisplay still image. This thinning-out is conceptually presented byillustrating the readout region shown in FIG. 7 as being smaller thanthe readout region shown in FIG. 5. However, the size ratio between thetwo readout regions does not limit the thinning-out rate. As shown inFIG. 7, the image capturing apparatus 100 performs read-out based on theY scheme with respect to some rows in the readout region (the rows beingdesignated as live image focusing pixels), and performs read-out basedon the X scheme with respect to the remaining rows. The system controlunit 50 generates a live display still image based on an image A+Bacquired from each pixel in the readout region. Also, the imagecapturing apparatus 100 calculates the amount of defocus based on imagesA and images B acquired from the pixels applied to the Y scheme. Thatis, the image capturing apparatus 100 can acquire focus detectionsignals (phase difference signals) in addition to an image signal forgenerating a live still image by performing still image capturing inaccordance with the scheme shown in FIG. 7.

FIG. 8 is a timing chart of the image capturing sequence B. In thesensor driving shown in FIG. 8, the hatched portions indicate theread-out based on the Y scheme. As shown in FIG. 8, a live display stillimage is captured between two instances of capturing a recording stillimage, and an image A and an image B for focusing processing areacquired at the time of capturing the live display still image. Also, atthe time of capturing a recording still image, read-out is performedbased on the X scheme with respect to all pixels in the readout regionso as to provide images A+B, and a recording still image is generatedfrom the obtained images A+B. The exposure time for a live display stillimage is shorter than that for a recording still image.

In the case of the image capturing sequence B, it is necessary tocapture a live display still image after a recording still image hasbeen captured, and thus the speed of continuous image capturing drops ascompared to that in the image capturing sequence A. Accordingly, interms of speed of continuous image capturing, the image capturingsequence A is superior to the image capturing sequence B. However, interms of image quality, the image capturing sequence B is superior tothe image capturing sequence A for the following three reasons.

Firstly, in the case of the image capturing sequence A, a noise leveldifference occurs in the recording still image, which may causedeterioration of image quality. To be specific, noise increases in theimage A+B acquired based on the Y scheme as compared to the image A+Bacquired based on the X scheme. For this reason, in the recording stillimage, a noise level difference occurs in the boundary between theregion applied to the X scheme and the region applied to the Y scheme.Particularly in the case of an image capturing condition in which alarge noise is generated (for example, in the case where the sensitivityis high), the noise level difference becomes significant, and the imagequality may deteriorate significantly. On the other hand, in the case ofthe image capturing sequence B, only the X scheme is used with respectto the recording still image, and it is therefore possible to preventdeterioration of image quality due to a noise level difference. Althougha noise level difference does not occur when all pixels in the readoutregion are read out based on the Y scheme in the image capturingsequence A, the noise in the entire still image increases. Accordingly,in any case, the image quality of the image capturing sequence A islower than the image quality of the image capturing sequence B.

Secondly, in the case of the image capturing sequence A, theaccumulation of the image A and the image B that is used for focuscontrol is performed by using an aperture value at the time of capturinga recording still image. For this reason, if the aperture value is setto a large value and the depth of field is deep, it may not be possibleto appropriately acquire the amount of defocus. As a result, theaccuracy of focusing decreases, and the image quality may deteriorate.On the other hand, in the case of the image capturing sequence B, bysetting a smaller aperture value at the time of capturing a live displaystill image, it is possible to establish a shallow depth of field andimprove the accuracy of focusing.

Thirdly, in the case of the image capturing sequence A, the length oftime between a timing of accumulation of the image A and the image Bthat is used for focus control and the next timing of accumulation (inother words, the timing of capturing the next recording still image) isrelatively long, and thus the focus cannot rapidly follow a movingsubject. For this reason, if the subject is moving fast, the accuracy offocusing decreases, which may cause deterioration of image quality. Onthe other hand, in the case of the image capturing sequence B, asdescribed above, a live display still image has a smaller number ofpixels than that of a recording still image, and thus the accumulationand the read-out for a live display still image are performed in ashorter time than the accumulation and the read-out for a recordingstill image. For this reason, the length of time between a timing ofaccumulation of the image A and the image B that is used for focuscontrol and a timing of capturing the next recording still image isshorter than that in the image capturing sequence A. Accordingly, thespeed at which the focus follows the subject is improved, and thedeterioration of image quality is suppressed.

In the image capturing sequence B, live displaying a still imagecaptured between two recording still images is not a requirement. Togeneralize it, in the image capturing sequence B, a still image (focusdetection still image) having a smaller number of pixels than that of arecording still image is captured between two recording still images.

In the present embodiment, at the time of continuous image capturing ofstill images, the image capturing apparatus 100 selects either the imagecapturing sequence A or the image capturing sequence B according to theimage capturing conditions (for example, sensitivity and aperture value)and the speed of the subject. In the case of the image capturingconditions and the speed of the subject in which a large image qualitydeterioration is highly likely to occur, the image capturing apparatus100 selects the image capturing sequence B so as to suppressdeterioration of image quality. Conversely, in the case of the imagecapturing conditions and the speed of the subject in which a large imagequality deterioration is less likely to occur, the image capturingapparatus 100 selects the image capturing sequence A so as to improvethe speed of continuous image capturing. A specific example of selectioncriteria will be described later with reference to FIG. 10.

In the present embodiment, the selection of the image capturing sequenceis not a requirement, and the image capturing apparatus 100 mayconstantly execute the image capturing sequence B. In this case,although the speed of continuous image capturing decreases, thedeterioration of image quality can be suppressed irrespectively of theimage capturing conditions and the speed of the subject. Also, theselection criteria for selection of the image capturing sequenceperformed by the image capturing apparatus 100 is not limited to theimage capturing conditions and the speed of the subject described above.For example, the image capturing apparatus 100 may select the imagecapturing sequence A or the image capturing sequence B in accordancewith an instruction from a user.

Next, continuous image capturing processing performed by the imagecapturing apparatus 100 will be described with reference to FIG. 9.Unless otherwise stated, the processing in each step in the flowchartshown in FIG. 9 is implemented by the system control unit 50 executing aprogram stored in the non-volatile memory 56. The processing of theflowchart starts in response to the user operating the mode changeswitch 60 to set the image capturing apparatus 100 in the continuousimage capturing mode.

In step S901, the system control unit 50 waits for the second shutterswitch 64 to be ON. If the second shutter switch 64 is set to ON, thesystem control unit 50 advances the processing to step S902. In stepS902, the system control unit 50 selects the image capturing sequence Aor the image capturing sequence B according to the image capturingconditions and the speed of the subject. The selection processing willbe described later in detail with reference to FIG. 10. In step S903,the system control unit 50 determines which of the image capturingsequence A and the image capturing sequence B has been selected in stepS902. If it is determined that the image capturing sequence A has beenselected, the system control unit 50 advances the processing to stepS904, and if it is determined that the image capturing sequence B hasbeen selected, the system control unit 50 advances the processing tostep S907.

In step S904, the system control unit 50 captures a recording stillimage based on the X/Y scheme, and records the captured image in therecording medium 200. The specific capturing method is as describedabove with reference to FIGS. 5 and 6. The system control unit 50temporarily stores the image A and the image B acquired at the time ofimage capturing in the memory 32. In step S905, the system control unit50 performs focus control on the subject by calculating the amount ofdefocus by using the image A and the image B, and driving the focus lensof the shooting lens 103. In step S906, the system control unit 50determines whether or not the continuous image capturing has beenfinished. It is determined that the continuous image capturing has beenfinished if, for example, a predetermined number of recording stillimages have been made, or if the second shutter switch 64 is turned off.If it is determined that the continuous image capturing has beenfinished, the processing of the flowchart ends. Otherwise, the systemcontrol unit 50 returns the processing to step S903. In this way,recording still images are continuously captured.

On the other hand, if it is determined in step S902 that the imagecapturing sequence B has been selected, the system control unit 50advances the processing from step S903 to step S907. In step S907, thesystem control unit 50 captures a recording still image based on the Xscheme, and records the captured recording still image in the recordingmedium 200. The specific capturing method is as described above withreference to FIG. 8, and all pixels in the readout region are read outbased on the X scheme. In step S908, the system control unit 50 acquiresaperture conditions for capturing a recording still image, anddetermines whether or not the aperture value is greater than or equal toa threshold value.

If it is determined in step S908 that the aperture value is less thanthe threshold value (if the aperture is close to an open state), thesystem control unit 50 advances the processing to step S909. In stepS909, the system control unit 50 captures a live display still imagebased on the X/Y scheme, and displays the captured live display stillimage on the display unit 28. The specific capturing method is asdescribed above with reference to FIGS. 7 and 8. The system control unit50 temporarily stores the image A and the image B acquired at the timeof image capturing in the memory 32. The system control unit 50 maydetermine the positions and the number of pixels that are to be read outbased on the Y scheme according to a criterion (for example, the stateof the subject) each time image capturing is performed in step S909. Itis thereby possible to further enhance the accuracy of focusing.

If it is determined in step S908 that the aperture value is greater thanor equal to the threshold value, the system control unit 50 advances theprocessing to step S910. In step S910, the system control unit 50 opensthe aperture to capture a live display still image based on the X/Yscheme, and displays the captured live display still image on thedisplay unit 28. The image capturing here is performed in the samemanner as that performed in step S909. That is, the processing in stepS910 is the same as that in step S909 except that the aperture is openedbefore image capturing is performed. As described above, if the aperturevalue is set to a large value, the depth of field is deep, and it maynot be possible to appropriately acquire the amount of defocus, and forthis reason, the processing of opening the aperture is performed if theaperture value is greater than or equal to the threshold value. Notethat the accuracy of focusing is improved more as the aperture is openedwider (in other words, as the aperture value is set to a smaller value),but a certain level of effect can be expected even if the aperture isslightly opened. For this reason, there is no particular limitation onthe degree of opening of the aperture in step S910.

After step S909 or step S910, the system control unit 50 advances theprocessing to step S905. The processing of step S905 is the same as thatin the case of the image capturing sequence A, but the image A and theimage B acquired at the time of capturing the live display still imageare used to calculate the amount of defocus. After that, the systemcontrol unit 50 alternately captures recording still images and livedisplay still images until completion of the continuous image capturing

Next, the image capturing sequence selection processing performed instep S902 shown in FIG. 9 will be described in detail with reference toFIG. 10. In step S1001, the system control unit 50 determines whether ornot the sensitivity for capturing a recording still image is greaterthan or equal to a threshold value. If it is determined that thesensitivity is greater than or equal to the threshold value (highsensitivity), the system control unit 50 advances the processing to stepS1005, and selects the image capturing sequence B. If it is determinedthat the sensitivity is less than the threshold value (low sensitivity),the system control unit 50 advances the processing to step S1002, anddetermines whether or not the aperture value is greater than or equal toa threshold value. If it is determined that the aperture value isgreater than or equal to the threshold value (close side), the systemcontrol unit 50 advances the processing to step S1005, and selects theimage capturing sequence B. If it is determined that the aperture valueis less than the threshold value (open side), the system control unit 50advances the processing to step S1003, performs detection of a subjectmotion, and determines whether or not the speed of the subject isgreater than or equal to a threshold value. In the detection of asubject motion, for example, the system control unit 50 can acquire anamount of change in the position of the center of gravity of a primarysubject region between frames based on the signal data output from theimage capturing unit 22 and detect a change in the state of the subjectfrom the acquired amount of change. An algorithm that determines whetheror not a primary subject is present within a screen based on luminanceor color area distribution, edge information, and the like within thescreen is generally known for detecting a primary subject. If the speedof the subject is greater than or equal to a threshold value (highspeed), the system control unit 50 advances the processing to stepS1005, and selects the image capturing sequence B. If the speed of thesubject is less than the threshold value (low speed), the system controlunit 50 advances the processing to step S1004, and selects the imagecapturing sequence A.

Although in step S1001 shown in FIG. 10, the sensitivity for capturing arecording still image is used as an example of the image capturingconditions that have an influence on noise, but the present embodimentis not limited thereto. Other examples of the image capturing conditionsinclude whether or not to execute black subtraction processing, thetemperature, the exposure time and the like for capturing a recordingstill image. The image capturing apparatus 100 selects the imagecapturing sequence A when an expected noise level based on one or anycombination of these image capturing conditions is low (first level),and selects the image capturing sequence B when the expected noise levelis high (second level).

Also, in general, the image quality level required for a live displaystill image is lower than that for a recording still image. However,depending on the noise level, the noise level difference in the livedisplay still image displayed in real time during continuous imagecapturing becomes significant, and the user may strongly feel thedeterioration of image quality. To address this, the image capturingapparatus 100 may further divide the expected noise level correspondingto the image capturing sequence B into two stages, and change the methodfor capturing a live display still image in step S909 and step S910according to the expected noise level. In this case, the image capturingapparatus 100 selects the image capturing sequence A when the expectednoise level is low (first level), and selects the image capturingsequence B when the expected noise level is moderate (second level) orhigh (third level). In capturing a live display still image based on theimage capturing sequence B (step S909 or step S910), the image capturingapparatus 100 uses the X/Y scheme if the expected noise level ismoderate (second level), and uses the Y scheme if the expected noiselevel is high (third level). Hereinafter, a specific example will begiven with reference to FIGS. 11 to 13.

In FIGS. 11 to 13, “A” represents the image capturing sequence A, and“B1” represents the image capturing sequence B in which a live displaystill image is captured based on the X/Y scheme (hereinafter alsoreferred to as “the image capturing sequence B1”). Likewise, “B2”represents the image capturing sequence B in which a live display stillimage is captured based on the Y scheme (hereinafter also referred to as“the image capturing sequence B2”).

FIG. 11 is a diagram showing an example of selecting an image capturingsequence based on sensitivity. In the example shown in FIG. 11, theimage capturing sequence A is selected if the sensitivity is less thanor equal to ISO 400. Then, in ISO 800 in which the noise leveldifference in the recording still image is noticeable, the imagecapturing sequence is switched from the image capturing sequence A tothe image capturing sequence B1. Furthermore, in ISO 3200 in which thenoise level difference in the live display still image is noticeable,the image capturing sequence is switched from the image capturingsequence B1 to the image capturing sequence B2.

FIG. 12 is a diagram showing an example of selecting an image capturingsequence based on whether or not to execute black subtractionprocessing, sensitivity and temperature. The black subtractionprocessing is processing for the purpose of correction of defectivepixels and removal of shading. It is known that when the blacksubtraction processing is performed, the captured image has a largenoise. In the example shown in FIG. 12, it is determined whether or notthe black subtraction processing is to be executed according to thesensitivity and the temperature. In the case of image capturingconditions corresponding to the blank cells, the black subtractionprocessing is not executed. In this case, for example, the imagecapturing sequence is selected in accordance with FIG. 11. In the caseof image capturing conditions corresponding to the cells with “A”, “B1”and “B2”, the black subtraction processing is executed. In this case, inISO 400 in which the noise level difference in the recording still imageis noticeable, the image capturing sequence is switched from the imagecapturing sequence A to the image capturing sequence B1. Furthermore, inISO 1600 in which the noise level difference in the live display stillimage is noticeable, the image capturing sequence is switched from theimage capturing sequence B1 to the image capturing sequence B2. Acomparison between FIG. 11 and FIG. 12 shows that when the blacksubtraction processing is performed, switching of the image capturingsequence is performed at a lower sensitivity. This is because if thesensitivity is the same, the expected noise level is higher when theblack subtraction processing is performed than when the blacksubtraction processing is not performed.

FIG. 13 is a diagram showing an example of selecting an image capturingsequence based on exposure time and temperature. The noise tends to belarger as the exposure time is longer and the temperature is higher. Forthis reason, in the example shown in FIG. 13, the image capturingsequence is switched in the following order as the exposure time islonger and the temperature is higher: the image capturing sequence A→theimage capturing sequence B1→the image capturing sequence B2.

As described above, according to the first embodiment, upon selection ofthe image capturing sequence B at the time of continuous imagecapturing, the image capturing apparatus 100 alternately captures arecording still image and a focus detection still image having a smallernumber of pixels than the recording still image. Then, the imagecapturing apparatus 100 captures the recording still images based on theX scheme, and captures the focus detection still images based on the X/Yscheme or the Y scheme. With this configuration, it is possible tosuppress deterioration of image quality of the recording still images.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-079735, filed Apr. 12, 2016, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image capturing apparatus comprising: an imagesensor including a plurality of pixels, each pixel including a pluralityof photoelectric conversion units that generate focus detection signalsfrom light flux that have passed through different regions in an exitpupil in an optical system; and an image capturing unit configured tocontinuously capture a plurality of images by using the image sensor,the image capturing unit being configured to acquire a signal in a firstacquisition mode or a second acquisition mode for each pixel, the firstacquisition mode being a mode in which an image signal obtained byadding the focus detection signals of the plurality of photoelectricconversion units is acquired, and the second acquisition mode being amode in which the focus detection signals are acquired in addition tothe image signal, wherein the image capturing unit is configured toalternately capture a recording image and a focus detection image havinga smaller number of pixels than the recording image, apply all pixels tothe first acquisition mode when capturing the recording image, and applyat least a part of the pixels to the second acquisition mode whencapturing the focus detection image.
 2. The image capturing apparatusaccording to claim 1, further comprising a selecting unit configured toselect a first continuous image capturing mode or a second continuousimage capturing mode based on a predetermined condition, wherein theimage capturing unit is configured to, if the first continuous imagecapturing mode is selected, continuously capture the recording image andapply at least a part of the pixels to the second acquisition mode whencapturing the recording image, and the image capturing unit isconfigured to, if the second continuous image capturing mode isselected, alternately capture the recording image and the focusdetection image, apply all pixels to the first acquisition mode whencapturing the recording image, and apply at least a part of the pixelsto the second acquisition mode when capturing the focus detection image.3. The image capturing apparatus according to claim 2, wherein theselecting unit is configured to select the first continuous imagecapturing mode if an expected noise level based on an image capturingcondition is a first level, and select the second continuous imagecapturing mode if the expected noise level is a second level that ishigher than the first level.
 4. The image capturing apparatus accordingto claim 3, wherein the image capturing condition includes at least oneof sensitivity, whether or not to execute black subtraction processing,temperature, and exposure time for capturing the recording image.
 5. Theimage capturing apparatus according to claim 2, wherein the selectingunit is configured to select the first continuous image capturing modeif an aperture value for capturing the recording image is less than athreshold value, and select the second continuous image capturing modeif the aperture value for capturing the recording image is greater thanor equal to the threshold value, and the image capturing unit isconfigured to, if the second continuous image capturing mode isselected, set an aperture value for capturing the focus detection imageto be smaller than the aperture value for capturing the recording image.6. The image capturing apparatus according to claim 2, furthercomprising a detection unit configured to detect a speed of a subject,wherein the selecting unit is configured to select the first continuousimage capturing mode if the speed of the subject is less than athreshold value, and select the second continuous image capturing modeif the speed of the subject is greater than or equal to the thresholdvalue.
 7. The image capturing apparatus according to claim 1, furthercomprising a display unit configured to display the focus detectionimage in real time.
 8. The image capturing apparatus according to claim2, further comprising a display unit configured to display the focusdetection image in real time, wherein the selecting unit is configuredto select the first continuous image capturing mode if an expected noiselevel based on an image capturing condition is a first level, and selectthe second continuous image capturing mode if the expected noise levelis a second level that is higher than the first level or a third levelthat is higher than the second level, and when capturing the focusdetection image in the second continuous image capturing mode, the imagecapturing unit is configured to: apply a part of the pixels to thesecond acquisition mode if the expected noise level is the second level;and apply all pixels to the second acquisition mode if the expectednoise level is the third level.
 9. The image capturing apparatusaccording to claim 8, wherein the image capturing condition includes atleast one of sensitivity, whether or not to execute black subtractionprocessing, temperature, and exposure time for capturing the recordingimage.
 10. The image capturing apparatus according to claim 1, whereinan exposure time for the focus detection image is shorter than anexposure time for the recording image.
 11. The image capturing apparatusaccording to claim 1, wherein the image capturing unit is configured to,if a part of the pixels is applied to the second acquisition mode whencapturing the focus detection image, determine a position and a numberof the part of the pixels each time image capturing is performed.
 12. Animage capturing apparatus comprising: an image sensor configured tooutput an image signal for generating an image and a focus detectionsignal for performing focus detection; and a controller configured tocontrol a number of pixels used to output the image signal and the focusdetection signal from the image sensor and a predetermined region foroutputting the focus detection signal in the image sensor, wherein thecontroller, when successively acquiring first frames for recording fromthe image sensor, controls the number of pixels used to output the imagesignal and the focus detection signal from the image sensor in a secondframe acquired between the successively acquired first frames, based onan image capturing condition, and the controller performs control so asto not record the second frame acquired between the successivelyacquired first frames if the second frame has a smaller number of pixelsthan the successively acquired first frames.
 13. The image capturingapparatus according to claim 12, wherein the control unit is configuredto perform control so as to record the successively acquired firstframes and the second frame acquired between the successively acquiredfirst frames if the second frame has an equal number of pixels to thesuccessively acquired first frames.
 14. The image capturing apparatusaccording to claim 12, wherein the control unit is configured to performcontrol so as to not read the focus detection signal with respect to thesuccessively acquired first frames if the second frame acquired betweenthe successively acquired first frames has a smaller number of pixelsthan the successively acquired first frames.
 15. An image capturingmethod for an image capturing apparatus comprising an image sensorincluding a plurality of pixels, each pixel including a plurality ofphotoelectric conversion units that generate focus detection signalsfrom light flux that have passed through different regions in an exitpupil in an optical system, the method comprising: continuouslycapturing a plurality of images by using the image sensor, wherein asignal is acquired in a first acquisition mode or a second acquisitionmode for each pixel, the first acquisition mode being a mode in which animage signal obtained by adding the focus detection signals of theplurality of photoelectric conversion units is acquired, and the secondacquisition mode being a mode in which the focus detection signals areacquired in addition to the image signal, wherein a recording image anda focus detection image having a smaller number of pixels than therecording image are alternately captured, all pixels are applied to thefirst acquisition mode when capturing the recording image, and at leasta part of the pixels are applied to the second acquisition mode whencapturing the focus detection image.
 16. An image capturing method foran image capturing apparatus comprising an image sensor configured tooutput an image signal for generating an image and a focus detectionsignal for performing focus detection, the method comprising:controlling a number of pixels used to output the image signal and thefocus detection signal from the image sensor and a predetermined regionfor outputting the focus detection signal in the image sensor, wherein,when first frames are successively acquired from the image sensor, thenumber of pixels used to output the image signal and the focus detectionsignal from the image sensor in a second frame acquired between thesuccessively acquired first frames is controlled based on an imagecapturing condition, and the second frame acquired between thesuccessively acquired first frames is not recorded if the second framehas a smaller number of pixels than the successively acquired firstframes.
 17. An image capturing apparatus comprising: an image sensorincluding a plurality of pixels, each pixel including a plurality ofphotoelectric conversion units that generate focus detection signalsfrom light flux that have passed through different regions in an exitpupil in an optical system; and a processor and a memory which functionas: an image capturing unit configured to continuously capture aplurality of images by using the image sensor, the image capturing unitbeing configured to acquire a signal in a first acquisition mode or asecond acquisition mode for each pixel, the first acquisition mode beinga mode in which an image signal obtained by adding the focus detectionsignals of the plurality of photoelectric conversion units is acquired,and the second acquisition mode being a mode in which the focusdetection signals are acquired in addition to the image signal, whereinthe image capturing unit is configured to alternately capture arecording image and a focus detection image having a smaller number ofpixels than the recording image, apply all pixels to the firstacquisition mode when capturing the recording image, and apply at leasta part of the pixels to the second acquisition mode when capturing thefocus detection image.
 18. The image capturing apparatus according toclaim 17, wherein the processor and the memory further function as: aselecting unit configured to select a first continuous image capturingmode or a second continuous image capturing mode based on apredetermined condition, wherein the image capturing unit is configuredto, if the first continuous image capturing mode is selected,continuously capture the recording image and apply at least a part ofthe pixels to the second acquisition mode when capturing the recordingimage, and the image capturing unit is configured to, if the secondcontinuous image capturing mode is selected, alternately capture therecording image and the focus detection image, apply all pixels to thefirst acquisition mode when capturing the recording image, and apply atleast a part of the pixels to the second acquisition mode when capturingthe focus detection image.
 19. The image capturing apparatus accordingto claim 18, wherein the selecting unit is configured to select thefirst continuous image capturing mode if an expected noise level basedon an image capturing condition is a first level, and select the secondcontinuous image capturing mode if the expected noise level is a secondlevel that is higher than the first level.
 20. The image capturingapparatus according to claim 12, wherein the first frames are frames forrecording still images, and the second frame is a frame for a livedisplay still image.
 21. The image capturing apparatus according toclaim 12, wherein the controller performs control such that the secondframe acquired between the successively acquired first frames has asmaller number of pixels than the successively acquired first frames,thereby reducing noise generated in the image sensor.